AbstractUnit disk graphs form a natural model for cellular radio channel assignment problems under the assumption of equally powerful, omnidirectional transmitters located on a uniform, flat plane. Here, we introduce and give motivation for an extension of this model, namely, sectorization at transmitter sites. We define and analyze properties of one case of sectorization, bisectored unit disk graphs, in particular, investigating properties concerning their chromatic number. Finally, we provide some experimental evidence to draw comparisons between graphs of this model and other classes of graphs. © 2004 Wiley Periodicals, Inc.